Heretofore, glass has been widely used as a material for use in making containers for seasoning, oil, juice, carbonated beverage, beer, Japanese sake, cosmetics, detergents, etc. Because of high production costs, empty glass containers after use are recovered and recycled for reuse. The above procedure, however, involved such drawbacks that because glass containers are heavy in weight, transport expenses thereof increase and in addition, they are liable to break and also cause inconvenience to handling thereof.
With the view of eliminating such drawbacks associated with the use of glass containers as mentioned above, various attempts have rapidly been made recently to convert the use of containers from glass containers to plastic containers. As materials for plastic containers, there are employed various kinds of plastics, polyethylene terephthalates are employed, because of their excellent mechanical strength, heat resistance, transparency and gas barrier properties, as a material for making containers to contain juice, refrigerant beverage, carbonated beverage, seasoning, detergent, cosmetics, etc. Of these plastic materials, polyethylene terephthalates are employed, because of their excellent mechanical strength, heat resistance, transparency and gas barrier properties, as a material for containers to contain juice, refrigerant beverage, carbonated beverage, seasoning, detergent, cosmetics, etc. Of these uses, particularly blow molded containers for filling juice, refrigerant beverage and carbonated beverage are required to be undergo sterilization and high speed filling operations and, on that account, such blow molded containers are required to be molded from heat resistant resins capable of withstanding the high speed filling and also required to have transparency.
Accordingly, as process for forming heat resistant blow molded containers from polyethylene terephthalates, there have heretofore been proposed a process for lamination such heat resistant resins as polyarylates on containers molded from polyethylene terephthalates [Plastics, Vol. 36 (No. 9), 121. (1985)], a process comprising subjecting containers molded from polyethylene terephthalates to heat setting (Japanese Patent Publn. No. 3301/1984, Japanese Patent L-O-P Publns. Nos. 12031/1980, 75833/1981 and 13142/1981) and a process comprising subjecting containers molded from polyethylene terephthalates to solvent treatment, thereby improving crystallinity index thereof (Japanese Patent Publn. No. 15807/1984). These processes referrred to above are all intended to impart heat-resisting properties by molding means or treatment after molding to polyethylene terephthalates which are originally insufficient in heat resistance. However, blow molded containers obtained by any of these processes fail to satisfy heat resistance at the time of high temperature filling and also transparency as desired. Therefore, earnestly desired is an advent of polyethylene terephthalates capable of withstanding the temperature, pressure and liquid weight at the time of high temperature filling and being excellent in heat resistance and transparency, and of preforms for blow molded articles as well as blow molded containers molded from such polyethylene terephthalates as mentioned above.